Remove //base dependency from sky_snapshot (#2872)

DEPS

@@ -53,7 +53,7 @@ deps = {
    Var('fuchsia_git') + '/ftl' + '@' + 'e9ebb15d179fed9467e5fb3ce6fb807cc4ad9a8b',
 
   'src/lib/tonic':
-   Var('fuchsia_git') + '/tonic' + '@' + '18fa4dec7495e0bafc9e3e6c1783e726c032d987',
+   Var('fuchsia_git') + '/tonic' + '@' + '325db6a9d6d32351e86843e5db0dfaad5f8651bf',
 
   'src/third_party/gtest':
    Var('fuchsia_git') + '/third_party/gtest' + '@' + 'c00f82917331efbbd27124b537e4ccc915a02b72',

sky/tools/sky_snapshot/BUILD.gn

@@ -4,25 +4,16 @@
 
 executable("sky_snapshot") {
   sources = [
-    "loader.cc",
-    "loader.h",
-    "logging.cc",
-    "logging.h",
     "main.cc",
-    "scope.h",
-    "switches.cc",
-    "switches.h",
-    "vm.cc",
-    "vm.h",
   ]
 
   deps = [
-    "//base",
     "//dart/runtime:libdart",
     "//dart/runtime/vm:libdart_platform",
-    "//lib/tonic/parsers",
+    "//lib/ftl",
+    "//lib/tonic/converter",
+    "//lib/tonic/file_loader",
     "//sky/engine/bindings:snapshot_cc",
-    "//third_party/zlib",
   ]
 
   if (!is_ios && !is_mac) {

sky/tools/sky_snapshot/loader.cc

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "sky/tools/sky_snapshot/loader.h"
-
-#include <memory>
-
-#include "base/command_line.h"
-#include "base/files/file_path.h"
-#include "base/files/file_util.h"
-#include "base/logging.h"
-#include "base/strings/string_util.h"
-#include "lib/tonic/parsers/packages_map.h"
-#include "sky/tools/sky_snapshot/logging.h"
-#include "sky/tools/sky_snapshot/scope.h"
-#include "sky/tools/sky_snapshot/switches.h"
-
-namespace {
-
-// Extract the scheme prefix ('package:' or 'file:' from )
-static std::string ExtractSchemePrefix(std::string url) {
-  if (base::StartsWithASCII(url, "package:", true)) {
-    return "package:";
-  } else if (base::StartsWithASCII(url, "file:", true)) {
-    return "file:";
-  }
-  return "";
-}
-
-// Extract the path from a package: or file: url.
-static std::string ExtractPath(std::string url) {
-  if (base::StartsWithASCII(url, "package:", true)) {
-    base::ReplaceFirstSubstringAfterOffset(&url, 0, "package:", "");
-  } else if (base::StartsWithASCII(url, "file:", true)) {
-    base::ReplaceFirstSubstringAfterOffset(&url, 0, "file:", "");
-  }
-  return url;
-}
-
-base::FilePath SimplifyPath(const base::FilePath& path) {
-  std::vector<base::FilePath::StringType> components;
-  path.GetComponents(&components);
-  auto it = components.begin();
-  base::FilePath result(*it++);
-  for (; it != components.end(); it++) {
-    auto& component = *it;
-    if (component == base::FilePath::kCurrentDirectory)
-      continue;
-    if (component == base::FilePath::kParentDirectory)
-      result = result.DirName();
-    else
-      result = result.Append(component);
-  }
-  return result;
-}
-
-class Loader {
- public:
-  Loader();
-
-  void LoadPackagesMap(const base::FilePath& packages);
-
-  const std::set<std::string>& dependencies() const { return dependencies_; }
-
-  Dart_Handle CanonicalizeURL(Dart_Handle library, Dart_Handle url);
-  base::FilePath GetFilePathForURL(std::string url);
-  base::FilePath GetFilePathForPackageURL(std::string url);
-  base::FilePath GetFilePathForFileURL(std::string url);
-  std::string Fetch(const std::string& url, std::string* resolved_url);
-  Dart_Handle Import(Dart_Handle url);
-  Dart_Handle Source(Dart_Handle library, Dart_Handle url);
-
-  void set_package_root(const base::FilePath& package_root) {
-    package_root_ = package_root;
-  }
-
- private:
-  std::set<std::string> dependencies_;
-  base::FilePath packages_;
-  base::FilePath package_root_;
-  std::unique_ptr<tonic::PackagesMap> packages_map_;
-
-  DISALLOW_COPY_AND_ASSIGN(Loader);
-};
-
-Loader::Loader() {}
-
-void Loader::LoadPackagesMap(const base::FilePath& packages) {
-  packages_ = packages;
-  dependencies_.insert(packages_.AsUTF8Unsafe());
-  std::string packages_source;
-  if (!base::ReadFileToString(packages_, &packages_source)) {
-    fprintf(stderr, "error: Unable to load .packages file '%s'.\n",
-            packages_.AsUTF8Unsafe().c_str());
-    exit(1);
-  }
-  packages_map_.reset(new tonic::PackagesMap());
-  std::string error;
-  if (!packages_map_->Parse(packages_source, &error)) {
-    fprintf(stderr, "error: Unable to parse .packages file '%s'.\n%s\n",
-            packages_.AsUTF8Unsafe().c_str(), error.c_str());
-    exit(1);
-  }
-}
-
-Dart_Handle Loader::CanonicalizeURL(Dart_Handle library, Dart_Handle url) {
-  std::string string = StringFromDart(url);
-  if (base::StartsWithASCII(string, "dart:", true))
-    return url;
-  if (base::StartsWithASCII(string, "package:", true))
-    return url;
-  if (base::StartsWithASCII(string, "file:", true)) {
-    base::ReplaceFirstSubstringAfterOffset(&string, 0, "file:", "");
-    return StringToDart(string);
-    ;
-  }
-
-  std::string library_url = StringFromDart(Dart_LibraryUrl(library));
-  std::string prefix = ExtractSchemePrefix(library_url);
-  std::string path = ExtractPath(library_url);
-  base::FilePath base_path(path);
-  base::FilePath resolved_path = base_path.DirName().Append(string);
-  base::FilePath normalized_path = SimplifyPath(resolved_path);
-  return StringToDart(prefix + normalized_path.AsUTF8Unsafe());
-}
-
-base::FilePath Loader::GetFilePathForURL(std::string url) {
-  if (base::StartsWithASCII(url, "package:", true))
-    return GetFilePathForPackageURL(url);
-  if (base::StartsWithASCII(url, "file:", true))
-    return GetFilePathForFileURL(url);
-
-  return base::FilePath(url);
-}
-
-base::FilePath Loader::GetFilePathForPackageURL(std::string url) {
-  DCHECK(base::StartsWithASCII(url, "package:", true));
-  base::ReplaceFirstSubstringAfterOffset(&url, 0, "package:", "");
-  size_t slash = url.find('/');
-  if (slash == std::string::npos)
-    return base::FilePath();
-  std::string package = url.substr(0, slash);
-  std::string library_path = url.substr(slash + 1);
-  std::string package_path = packages_map_->Resolve(package);
-  if (package_path.empty())
-    return base::FilePath();
-  if (base::StartsWithASCII(package_path, "file://", true)) {
-    base::ReplaceFirstSubstringAfterOffset(&package_path, 0, "file://", "");
-    return base::FilePath(package_path + library_path);
-  }
-  return packages_.DirName().Append(package_path).Append(library_path);
-}
-
-base::FilePath Loader::GetFilePathForFileURL(std::string url) {
-  DCHECK(base::StartsWithASCII(url, "file://", true));
-  base::ReplaceFirstSubstringAfterOffset(&url, 0, "file://", "");
-  return base::FilePath(url);
-}
-
-std::string Loader::Fetch(const std::string& url, std::string* resolved_url) {
-  base::FilePath path = GetFilePathForURL(url);
-  base::FilePath absolute_path = base::MakeAbsoluteFilePath(path);
-  *resolved_url = "file://" + absolute_path.value();
-  std::string source;
-  if (!base::ReadFileToString(absolute_path, &source)) {
-    fprintf(stderr, "error: Unable to find Dart library '%s'.\n", url.c_str());
-    exit(1);
-  }
-  dependencies_.insert(path.AsUTF8Unsafe());
-  return source;
-}
-
-Dart_Handle Loader::Import(Dart_Handle url) {
-  std::string resolved_url;
-  Dart_Handle source = StringToDart(Fetch(StringFromDart(url), &resolved_url));
-  Dart_Handle result =
-      Dart_LoadLibrary(url, StringToDart(resolved_url), source, 0, 0);
-  LogIfError(result);
-  return result;
-}
-
-Dart_Handle Loader::Source(Dart_Handle library, Dart_Handle url) {
-  std::string resolved_url;
-  Dart_Handle source = StringToDart(Fetch(StringFromDart(url), &resolved_url));
-  Dart_Handle result =
-      Dart_LoadSource(library, url, StringToDart(resolved_url), source, 0, 0);
-  LogIfError(result);
-  return result;
-}
-
-Loader* g_loader = nullptr;
-
-Loader& GetLoader() {
-  if (!g_loader) {
-    base::CommandLine& command_line = *base::CommandLine::ForCurrentProcess();
-    g_loader = new Loader();
-    if (command_line.HasSwitch(switches::kPackages)) {
-      g_loader->LoadPackagesMap(
-          command_line.GetSwitchValuePath(switches::kPackages));
-
-    } else if (command_line.HasSwitch(switches::kPackageRoot)) {
-      g_loader->set_package_root(
-          command_line.GetSwitchValuePath(switches::kPackageRoot));
-    } else {
-      fprintf(stderr, "error: Need either --packages or --package-root.\n");
-      exit(1);
-    }
-  }
-  return *g_loader;
-}
-
-}  // namespace
-
-Dart_Handle HandleLibraryTag(Dart_LibraryTag tag,
-                             Dart_Handle library,
-                             Dart_Handle url) {
-  CHECK(Dart_IsLibrary(library));
-  CHECK(Dart_IsString(url));
-
-  if (tag == Dart_kCanonicalizeUrl)
-    return GetLoader().CanonicalizeURL(library, url);
-
-  if (tag == Dart_kImportTag)
-    return GetLoader().Import(url);
-
-  if (tag == Dart_kSourceTag)
-    return GetLoader().Source(library, url);
-
-  return Dart_NewApiError("Unknown library tag.");
-}
-
-void LoadScript(const std::string& url) {
-  std::string resolved_url;
-  Dart_Handle source = StringToDart(GetLoader().Fetch(url, &resolved_url));
-  LogIfError(Dart_LoadScript(StringToDart(url), StringToDart(resolved_url),
-                             source, 0, 0));
-}
-
-const std::set<std::string>& GetDependencies() {
-  return GetLoader().dependencies();
-}

sky/tools/sky_snapshot/loader.h

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef SKY_TOOLS_SKY_SNAPSHOT_LOADER_H_
-#define SKY_TOOLS_SKY_SNAPSHOT_LOADER_H_
-
-#include <set>
-#include <string>
-
-#include "dart/runtime/include/dart_api.h"
-
-Dart_Handle HandleLibraryTag(Dart_LibraryTag tag,
-                             Dart_Handle library,
-                             Dart_Handle url);
-void LoadScript(const std::string& url);
-const std::set<std::string>& GetDependencies();
-
-#endif  // SKY_TOOLS_SKY_SNAPSHOT_LOADER_H_

sky/tools/sky_snapshot/logging.cc

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "sky/tools/sky_snapshot/logging.h"
-
-#include "base/logging.h"
-
-bool LogIfError(Dart_Handle handle) {
-  if (Dart_IsError(handle)) {
-    LOG(ERROR) << Dart_GetError(handle);
-
-    // Only unhandled exceptions have stacktraces.
-    if (!Dart_ErrorHasException(handle))
-      return true;
-
-    Dart_Handle stacktrace = Dart_ErrorGetStacktrace(handle);
-    const char* stacktrace_cstr = "";
-    Dart_StringToCString(Dart_ToString(stacktrace), &stacktrace_cstr);
-    LOG(ERROR) << stacktrace_cstr;
-    return true;
-  }
-  return false;
-}
-
-std::string StringFromDart(Dart_Handle string) {
-  CHECK(Dart_IsString(string));
-  uint8_t* utf8_array;
-  intptr_t length;
-  Dart_StringToUTF8(string, &utf8_array, &length);
-  return std::string(reinterpret_cast<const char*>(utf8_array), length);
-}
-
-Dart_Handle StringToDart(const std::string& string) {
-  return Dart_NewStringFromUTF8(reinterpret_cast<const uint8_t*>(string.data()),
-                                string.length());
-}

sky/tools/sky_snapshot/logging.h

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef SKY_TOOLS_SKY_SNAPSHOT_LOGGING_H_
-#define SKY_TOOLS_SKY_SNAPSHOT_LOGGING_H_
-
-#include <string>
-
-#include "dart/runtime/include/dart_api.h"
-
-bool LogIfError(Dart_Handle handle);
-std::string StringFromDart(Dart_Handle string);
-Dart_Handle StringToDart(const std::string& string);
-
-#endif  // SKY_TOOLS_SKY_SNAPSHOT_LOGGING_H_

sky/tools/sky_snapshot/main.cc

-// Copyright 2015 The Chromium Authors. All rights reserved.
+// Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <fcntl.h>
+
 #include <iostream>
+#include <set>
+#include <string>
 
-#include "base/at_exit.h"
-#include "base/basictypes.h"
-#include "base/command_line.h"
-#include "base/files/file_path.h"
-#include "base/files/file_util.h"
-#include "base/logging.h"
-#include "base/process/memory.h"
 #include "dart/runtime/include/dart_api.h"
-#include "sky/tools/sky_snapshot/loader.h"
-#include "sky/tools/sky_snapshot/logging.h"
-#include "sky/tools/sky_snapshot/scope.h"
-#include "sky/tools/sky_snapshot/switches.h"
-#include "sky/tools/sky_snapshot/vm.h"
+#include "lib/ftl/arraysize.h"
+#include "lib/ftl/command_line.h"
+#include "lib/ftl/files/directory.h"
+#include "lib/ftl/files/eintr_wrapper.h"
+#include "lib/ftl/files/file_descriptor.h"
+#include "lib/ftl/files/file.h"
+#include "lib/ftl/files/symlink.h"
+#include "lib/ftl/files/unique_fd.h"
+#include "lib/ftl/logging.h"
+#include "lib/tonic/converter/dart_converter.h"
+#include "lib/tonic/file_loader/file_loader.h"
+
+extern "C" {
+extern const uint8_t* kDartVmIsolateSnapshotBuffer;
+extern const uint8_t* kDartIsolateSnapshotBuffer;
+}
+
+namespace sky_snapshot {
+namespace {
+
+using tonic::ToDart;
+
+constexpr char kHelp[] = "help";
+constexpr char kPackages[] = "packages";
+constexpr char kSnapshot[] = "snapshot";
+constexpr char kDepfile[] = "depfile";
+constexpr char kBuildOutput[] = "build-output";
+
+const char* kDartArgs[] = {
+    // clang-format off
+    "--enable_mirrors=false",
+    "--load_deferred_eagerly=true",
+    "--conditional_directives",
+    // TODO(chinmaygarde): The experimental interpreter for iOS device targets
+    // does not support all these flags. The build process uses its own version
+    // of this snapshotter. Till support for all these flags is added, make
+    // sure the snapshotter does not error out on unrecognized flags.
+    "--ignore-unrecognized-flags",
+    // clang-format on
+};
 
 void Usage() {
-  std::cerr << R"USAGE(usage: sky_snapshot --packages=PACKAGES --snapshot=SNAPSHOT_BLOB <lib/main.dart>
-       [ --depfile=DEPS_FILE ] [ --build-output=BUILD_OUTPUT ] [ --help ]
-
- * PACKAGES is the '.packages' file that defines where to find Dart packages.
- * SNAPSHOT_BLOB is the file to write the snapshot into.
- * DEPS_FILE is an optional '.d' file to depedendency information into.
- * BUILD_OUTPUT optionally overrides the target name used in the DEPS_FILE.
-   (The default is SNAPSHOT_BLOB.)
-)USAGE";
+  std::cerr
+      << "Usage: sky_snapshot --" << kPackages << "=PACKAGES" << std::endl
+      << "                  [ --" << kSnapshot << "=OUTPUT_SNAPSHOT ]"
+      << std::endl
+      << "                  [ --" << kDepfile << "=DEPFILE ]" << std::endl
+      << "                  [ --" << kBuildOutput << "=BUILD_OUTPUT ]"
+      << std::endl
+      << std::endl
+      << "                        MAIN_DART" << std::endl
+      << " * PACKAGES is the '.packages' file that defines where to find Dart "
+         "packages."
+      << std::endl
+      << " * OUTPUT_SNAPSHOT is the file to write the snapshot into."
+      << std::endl
+      << " * DEPFILE is the file into which to write the '.d' depedendency "
+         "information into."
+      << std::endl
+      << " * BUILD_OUTPUT determines the target name used in the " << std::endl
+      << "   DEPFILE. (Required if DEPFILE is provided.) " << std::endl;
+}
+
+class DartScope {
+ public:
+  DartScope(Dart_Isolate isolate) {
+    Dart_EnterIsolate(isolate);
+    Dart_EnterScope();
+  }
+
+  ~DartScope() {
+    Dart_ExitScope();
+    Dart_ExitIsolate();
+  }
+};
+
+void InitDartVM() {
+  FTL_CHECK(Dart_SetVMFlags(arraysize(kDartArgs), kDartArgs));
+  char* error = Dart_Initialize(
+      kDartVmIsolateSnapshotBuffer, nullptr, nullptr, nullptr, nullptr, nullptr,
+      nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr);
+  if (error)
+    FTL_LOG(FATAL) << error;
+}
+
+Dart_Isolate CreateDartIsolate() {
+  FTL_CHECK(kDartIsolateSnapshotBuffer);
+  char* error = nullptr;
+  Dart_Isolate isolate =
+      Dart_CreateIsolate("dart:snapshot", "main", kDartIsolateSnapshotBuffer,
+                         nullptr, nullptr, &error);
+  FTL_CHECK(isolate) << error;
+  Dart_ExitIsolate();
+  return isolate;
+}
+
+tonic::FileLoader* g_loader = nullptr;
+
+tonic::FileLoader& GetLoader() {
+  if (!g_loader)
+    g_loader = new tonic::FileLoader();
+  return *g_loader;
 }
 
-void WriteSnapshot(base::FilePath path) {
-  uint8_t* buffer;
-  intptr_t size;
-  CHECK(!LogIfError(Dart_CreateScriptSnapshot(&buffer, &size)));
+Dart_Handle HandleLibraryTag(Dart_LibraryTag tag,
+                             Dart_Handle library,
+                             Dart_Handle url) {
+  FTL_CHECK(Dart_IsLibrary(library));
+  FTL_CHECK(Dart_IsString(url));
+  tonic::FileLoader& loader = GetLoader();
+  if (tag == Dart_kCanonicalizeUrl)
+    return loader.CanonicalizeURL(library, url);
+  if (tag == Dart_kImportTag)
+    return loader.Import(url);
+  if (tag == Dart_kSourceTag)
+    return loader.Source(library, url);
+  return Dart_NewApiError("Unknown library tag.");
+}
 
-  CHECK_EQ(base::WriteFile(path, reinterpret_cast<const char*>(buffer), size),
-           size);
+std::vector<char> CreateSnapshot() {
+  uint8_t* buffer = nullptr;
+  intptr_t size = 0;
+  DART_CHECK_VALID(Dart_CreateScriptSnapshot(&buffer, &size));
+  const char* begin = reinterpret_cast<const char*>(buffer);
+  return std::vector<char>(begin, begin + size);
 }
 
-void WriteDependencies(base::FilePath path,
-                       const std::string& build_output,
-                       const std::set<std::string>& deps) {
-  base::FilePath current_directory;
-  CHECK(base::GetCurrentDirectory(&current_directory));
+bool WriteDepfile(const std::string& path,
+                  const std::string& build_output,
+                  const std::set<std::string>& deps) {
+  std::string current_directory = files::GetCurrentDirectory();
   std::string output = build_output + ":";
-  for (const auto& i : deps) {
-    output += " ";
-    base::FilePath dep_path(i);
-    if (dep_path.IsAbsolute()) {
-      output += dep_path.MaybeAsASCII();
+  for (const auto& dep : deps) {
+    std::string file = dep;
+    FTL_DCHECK(!file.empty());
+    if (file[0] != '/')
+      file = current_directory + "/" + file;
+
+    std::string resolved_file;
+    if (files::ReadSymbolicLink(file, &resolved_file)) {
+      output += " " + resolved_file;
     } else {
-      output += current_directory.Append(dep_path).MaybeAsASCII();
+      output += " " + file;
     }
   }
-  const char* data = output.c_str();
-  const intptr_t data_length = output.size();
-  CHECK_EQ(base::WriteFile(path, data, data_length), data_length);
+  return files::WriteFile(path, output.data(), output.size());
 }
 
-int main(int argc, const char* argv[]) {
-  base::AtExitManager exit_manager;
-  base::EnableTerminationOnHeapCorruption();
-  base::CommandLine::Init(argc, argv);
-
-  const base::CommandLine& command_line =
-      *base::CommandLine::ForCurrentProcess();
-
-  if (command_line.HasSwitch(switches::kHelp) ||
-      command_line.GetArgs().empty()) {
+int CreateSnapshot(const ftl::CommandLine& command_line) {
+  if (command_line.HasOption(kHelp, nullptr)) {
     Usage();
     return 0;
   }
 
-  if (!command_line.HasSwitch(switches::kSnapshot)) {
-    fprintf(stderr, "error: Need --snapshot.\n");
-    exit(1);
+  if (command_line.positional_args().empty()) {
+    Usage();
+    return 1;
+  }
+
+  std::string packages;
+  if (!command_line.GetOptionValue(kPackages, &packages)) {
+    std::cerr << "error: Need --" << kPackages << std::endl;
+    return 1;
+  }
+
+  std::vector<std::string> args = command_line.positional_args();
+  if (args.size() != 1) {
+    std::cerr << "error: Need one position argument. Got " << args.size() << "."
+              << std::endl;
+    return 1;
+  }
+
+  std::string main_dart = args[0];
+
+  std::string snapshot;
+  if (!command_line.GetOptionValue(kSnapshot, &snapshot)) {
+    std::cerr << "error: Need --" << kSnapshot << "." << std::endl;
+    return 1;
+  }
+
+  std::string depfile;
+  std::string build_output;
+  if (command_line.GetOptionValue(kDepfile, &depfile) &&
+      !command_line.GetOptionValue(kBuildOutput, &build_output)) {
+    std::cerr << "error: Need --" << kBuildOutput << " if --" << kDepfile
+              << " is specified." << std::endl;
+    return 1;
   }
 
   InitDartVM();
+
+  tonic::FileLoader& loader = GetLoader();
+  if (!loader.LoadPackagesMap(packages))
+    return 1;
+
   Dart_Isolate isolate = CreateDartIsolate();
-  CHECK(isolate);
+  FTL_CHECK(isolate) << "Failed to create isolate.";
 
-  DartIsolateScope scope(isolate);
-  DartApiScope api_scope;
+  DartScope scope(isolate);
 
-  auto args = command_line.GetArgs();
-  CHECK(args.size() == 1);
-  LoadScript(args[0]);
+  DART_CHECK_VALID(Dart_SetLibraryTagHandler(HandleLibraryTag));
+  DART_CHECK_VALID(Dart_LoadScript(ToDart(main_dart), Dart_Null(),
+                                   ToDart(loader.Fetch(main_dart)), 0, 0));
 
-  if (LogIfError(Dart_FinalizeLoading(true)))
-    return 1;
+  std::vector<char> snapshot_blob = CreateSnapshot();
 
-  CHECK(command_line.HasSwitch(switches::kSnapshot));
-  WriteSnapshot(command_line.GetSwitchValuePath(switches::kSnapshot));
+  if (!snapshot.empty() &&
+      !files::WriteFile(snapshot, snapshot_blob.data(), snapshot_blob.size())) {
+    std::cerr << "error: Failed to write snapshot to '" << snapshot << "'."
+              << std::endl;
+    return 1;
+  }
 
-  if (command_line.HasSwitch(switches::kDepfile)) {
-    auto build_output = command_line.HasSwitch(switches::kBuildOutput) ?
-        command_line.GetSwitchValueASCII(switches::kBuildOutput) :
-        command_line.GetSwitchValueASCII(switches::kSnapshot);
-    WriteDependencies(command_line.GetSwitchValuePath(switches::kDepfile),
-                      build_output,
-                      GetDependencies());
+  if (!depfile.empty() &&
+      !WriteDepfile(depfile, build_output, loader.dependencies())) {
+    std::cerr << "error: Failed to write depfile to '" << depfile << "'."
+              << std::endl;
+    return 1;
   }
 
   return 0;
 }
+
+}  // namespace
+}  // namespace sky_snapshot
+
+int main(int argc, const char* argv[]) {
+  return sky_snapshot::CreateSnapshot(ftl::CommandLineFromArgcArgv(argc, argv));
+}

sky/tools/sky_snapshot/scope.h

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef SKY_TOOLS_SKY_SNAPSHOT_SCOPE_H_
-#define SKY_TOOLS_SKY_SNAPSHOT_SCOPE_H_
-
-#include "base/basictypes.h"
-#include "base/logging.h"
-#include "dart/runtime/include/dart_api.h"
-
-class DartIsolateScope {
- public:
-  explicit DartIsolateScope(Dart_Isolate isolate) {
-    CHECK(!Dart_CurrentIsolate());
-    Dart_EnterIsolate(isolate);
-  }
-  ~DartIsolateScope() { Dart_ExitIsolate(); }
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(DartIsolateScope);
-};
-
-class DartApiScope {
- public:
-  DartApiScope() { Dart_EnterScope(); }
-  ~DartApiScope() { Dart_ExitScope(); }
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(DartApiScope);
-};
-
-#endif  // SKY_TOOLS_SKY_SNAPSHOT_SCOPE_H_

sky/tools/sky_snapshot/switches.cc

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "sky/tools/sky_snapshot/switches.h"
-
-namespace switches {
-
-const char kBuildOutput[] = "build-output";
-const char kDepfile[] = "depfile";
-const char kHelp[] = "help";
-const char kPackages[] = "packages";
-const char kPackageRoot[] = "package-root";
-const char kSnapshot[] = "snapshot";
-
-}  // namespace switches

sky/tools/sky_snapshot/switches.h

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef SKY_TOOLS_SKY_SNAPSHOT_SWITCHES_H_
-#define SKY_TOOLS_SKY_SNAPSHOT_SWITCHES_H_
-
-namespace switches {
-
-extern const char kBuildOutput[];
-extern const char kDepfile[];
-extern const char kHelp[];
-extern const char kPackages[];
-extern const char kPackageRoot[];
-extern const char kSnapshot[];
-
-}  // namespace switches
-
-#endif  // SKY_TOOLS_SKY_SNAPSHOT_SWITCHES_H_

sky/tools/sky_snapshot/vm.cc

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "sky/tools/sky_snapshot/vm.h"
-
-#include "base/logging.h"
-#include "sky/tools/sky_snapshot/loader.h"
-#include "sky/tools/sky_snapshot/logging.h"
-
-#include <iostream>
-
-extern "C" {
-extern void* kDartVmIsolateSnapshotBuffer;
-extern void* kDartIsolateSnapshotBuffer;
-}
-
-static const char* kDartArgs[] = {
-    "--enable_mirrors=false",
-    "--load_deferred_eagerly=true",
-    "--conditional_directives",
-    // TODO(chinmaygarde): The experimental interpreter for iOS device targets
-    // does not support all these flags. The build process uses its own version
-    // of this snapshotter. Till support for all these flags is added, make
-    // sure the snapshotter does not error out on unrecognized flags.
-    "--ignore-unrecognized-flags",
-};
-
-void InitDartVM() {
-  CHECK(Dart_SetVMFlags(arraysize(kDartArgs), kDartArgs));
-  char* init_message = Dart_Initialize(
-      reinterpret_cast<uint8_t*>(&kDartVmIsolateSnapshotBuffer), nullptr,
-      nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
-      nullptr, nullptr, nullptr, nullptr);
-  if (init_message != nullptr) {
-    std::cerr << "Dart_Initialize Error: " << init_message << std::endl;
-    free(init_message);
-    CHECK(false);
-  }
-}
-
-Dart_Isolate CreateDartIsolate() {
-  CHECK(kDartIsolateSnapshotBuffer);
-  char* error = nullptr;
-  Dart_Isolate isolate = Dart_CreateIsolate(
-      "dart:snapshot", "main",
-      reinterpret_cast<uint8_t*>(&kDartIsolateSnapshotBuffer), nullptr, nullptr,
-      &error);
-
-  CHECK(isolate) << error;
-  CHECK(!LogIfError(Dart_SetLibraryTagHandler(HandleLibraryTag)));
-
-  Dart_ExitIsolate();
-  return isolate;
-}

sky/tools/sky_snapshot/vm.h

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef SKY_TOOLS_SKY_SNAPSHOT_VM_H_
-#define SKY_TOOLS_SKY_SNAPSHOT_VM_H_
-
-#include "dart/runtime/include/dart_api.h"
-
-void InitDartVM();
-Dart_Isolate CreateDartIsolate();
-
-#endif  // SKY_TOOLS_SKY_SNAPSHOT_VM_H_